This project is concerned with the maintenance and distribution of a cohesive and comprehensive database of information about restriction endonucleases and their associated methylases. REBASE has been in existence since 1975 and is currently implemented in a relational format under SYBASE. Information enters the database both from the published literature and by direct submission from the investigators either prior to publication or instead of publication. Approximately 11% of the entries are unpublished other than through REBASE. The information is disseminated throughout the world both by formal publication in the scientific literature and in a variety of electronic formats. Thus, monthly updates are posted and selected files distributed through an automatic email list to more than 350 sites. In addition, the information is available by anonymous FTP or through the World Wide Web. Among the files maintained and updated monthly are specialized ones that are used by many of the more widely used computer programs, such as GCG, MacVector, DNA Strider etc. These files are ready to use and include up-to-date information about the full range of specificities and their commercial availability. The information available through REBASE is key to all investigators planning experiments to cleave and/or religate DNA. It is a unique resource for the practice of Biotechnology and its contents are used directly or indirectly by many sections of the research health care community.